bryan-minimal · Oct 9, 2026 · Oct 8, 2026 · Oct 8, 2026
@@ -0,0 +1,73 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Karl Godard <karl@minimal.dev>
+Date: Thu, 8 Oct 2026 19:22:37 +0000
+Subject: [PATCH] virtio/vsock: refuse a stream whose unix proxy cannot be
+ created
+
+When the guest opens a stream to a vsock port mapped to a host unix
+socket with krun_add_vsock_port2(..., listen=false), process_op_request()
+creates the host leg with UnixProxy::new(...).unwrap(). UnixProxy::new()
+fails only when socket(AF_UNIX) fails (EMFILE, ENFILE, ENOBUFS, ENOMEM),
+a transient host condition, but the unwrap() turns it into a panic on the
+event-manager thread, and the panic aborts the whole VMM: every guest
+connection and the guest itself go down because one host socket could
+not be created.
+
+Refuse just that connection instead. Log the error, which carries the
+errno, and answer the guest with OP_RST, the same reply the function
+already sends when a guest connects to a port that is mapped for
+listening. Nothing is inserted into the proxy map, so there is no state
+to clean up, and the guest's connect() fails with ECONNRESET while the
+VM keeps running.
+
+The TSI stream and dgram proxy creation paths already handle this error;
+this was the only guest-triggered proxy construction that unwrapped it.
+
+Assisted-by: Claude Code: opus-5.5
+---
+ src/devices/src/virtio/vsock/muxer.rs | 22 +++++++++++++++++++---
+ 1 file changed, 19 insertions(+), 3 deletions(-)
+
+diff --git a/src/devices/src/virtio/vsock/muxer.rs b/src/devices/src/virtio/vsock/muxer.rs
+index 6cf8b6f..4cc56fd 100644
+--- a/src/devices/src/virtio/vsock/muxer.rs
++++ b/src/devices/src/virtio/vsock/muxer.rs
+@@ -560,7 +560,7 @@ impl VsockMuxer {
+                 }
+                 let rxq = self.rxq.clone();
+
+-                let mut unix = UnixProxy::new(
++                let mut unix = match UnixProxy::new(
+                     id,
+                     self.cid,
+                     pkt.dst_port(),
+@@ -569,8 +569,24 @@ impl VsockMuxer {
+                     queue.clone(),
+                     rxq,
+                     path.to_path_buf(),
+-                )
+-                .unwrap();
++                ) {
++                    Ok(unix) => unix,
++                    Err(e) => {
++                        // Creating the host socket can fail transiently (e.g.
 +                        // EMFILE, ENFILE, ENOBUFS). Refuse this connection
++                        // instead of taking the whole VM down.
++                        error!(
++                            "error creating unix proxy for port {}, sending rst: {e}",
++                            pkt.dst_port()
++                        );
++                        let rx = MuxerRx::Reset {
++                            local_port: pkt.dst_port(),
++                            peer_port: pkt.src_port(),
++                        };
++                        push_packet(self.cid, rx, &self.rxq, queue, mem);
++                        return;
++                    }
++                };
+                 let tsi = TsiConnectReq {
+                     peer_port: 0,
+                     addr: SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), 0).into(),
+-- 
+2.55.0
+
@@ -9,7 +9,7 @@ let pkgconf = import "../pkgconf/build.ncl" in
 let rust = import "../rust/build.ncl" in
 let toolchain = import "../toolchain/build.ncl" in
 
-let version = "1.19.4" in
+let version = "1.19.6" in
 {
   name = "libkrun",
 
@@ -39,9 +39,19 @@ let version = "1.19.4" in
     # fix lands in an upstream release we can pin.
     # https://github.com/gominimal/minimal/issues/869
     { file = "0001-vsock-bound-outstanding-packets.patch" } | Local,
+    # A guest-to-host vsock stream whose host unix socket cannot be created
+    # (EMFILE, ENFILE, ENOBUFS) hit UnixProxy::new(...).unwrap() in
+    # muxer.rs, and the panic aborted the whole VMM. The patch logs the error
+    # and answers that one stream with OP_RST instead, so the guest's
+    # connect() fails and the VM keeps running. 1.19.6 does not fix this.
+    #
+    # Identical to the patch gominimal/minimal carries at
+    # vendor/libkrun/patches/ (#2105); drop it once upstream releases the fix.
+    # https://github.com/gominimal/minimal/issues/2103
+    { file = "0002-vsock-refuse-stream-when-unix-proxy-creation-fails.patch" } | Local,
     {
       url = "https://github.com/containers/libkrun/archive/refs/tags/v%{version}.tar.gz",
-      sha256 = "e8775fab2b460972a67ca6cd936296bb79cdb078d852d712a283cb290dd0b284",
+      sha256 = "7025d72208172dc06f791ad5af7ccaafeabdac9869f74ccb45fb6d4f6e5991cd",
       extract = true,
       strip_prefix = "libkrun-%{version}",
     } | Source,

@@ -7,11 +7,12 @@ export CC=gcc
 export LD=gcc
 export RUSTFLAGS="-C linker=gcc --remap-path-prefix=$(pwd)=/builddir --remap-path-prefix=$HOME/.cargo=/cargo"
 
-# vsock fix (see build.ncl). Applied by explicit name, not by glob. `set -e`
+# vsock fixes (see build.ncl). Applied by explicit name, not by glob. `set -e`
 # plus patch's non-zero exit on a rejected hunk makes a stale patch abort the
 # build; a silently-skipped patch would publish a libkrun that looks fixed and
 # is not.
 patch -Np1 -i "0001-vsock-bound-outstanding-packets.patch"
+patch -Np1 -i "0002-vsock-refuse-stream-when-unix-proxy-creation-fails.patch"
 
 # BLK=1 enables virtio-blk (exports krun_add_disk2); `blk` is not a default
 # libkrun feature, so consumers fail to link without it.